The instability of vascular plasminogen activator extracted from the vascular trees of human cadavers is described by Aoki, J. Biol. Chem. (Tokyo), 75, 731 (1974). Aoki found that the activator was stabilized only by high sodium chloride concentrations, greater than about 0.5M.
Binder, et al. J. Biol. Chem. 254, 1998 (1979) describe the use of high salt and arginine containing buffers during a multi-step purification procedure as essential to maintain the activity of vascular plasminogen activator derived from human cadaver perfusates. The purification steps where carried out in the presence of 0.3 to 1.0M NaCl and 0.1M arginine.
Radcliffe et al., Arch. of Biochem. & Biophy. 189, 185 (1978) describe the separation of plasminogen activator from human plasma by chromotography on lysine-Sepharose. In one experiment, crude plasminogen activator from stabilized plasma was eluted from lysine-Sepharose using a gradient of 0M to 0.5M arginine in 0.6M NaCl.
Human tissue plasminogen activator derived from natural tissue source is described by Collen et al. in European Patent Application Publication No. 041766, published Dec. 16, 1981 based upon a first filing of June 11, 1980. The authors employed a purification scheme that affords tissue plasminogen activator at relatively high purity levels. Collen et al. studied the stability of preparations of their purified tissue plasminogen activator both in the liquid and lyophilized states, and found that the lyophilized forms were repeatedly unstable even when prepared from solutions containing 0.3M NaCl.
In order that materials like tissue plasminogen activator be provided to health care personnel and patients, these materials must be prepared as pharmaceutical compositions. Such compositions must be stable for appropriate periods of time, must be acceptable in their own right for administration to humans, and must be readily manufacturable. An example of such a composition would be a solution designed for parenteral administration. Although in many cases pharmaceutical solution formulations are provided in liquid form, appropriate for immediate use, such parenteral formulations may also be provided in frozen or in lyophilized form. In the former case, the composition must be thawed prior to use. The latter form is often used to enhance the stability of the medicinal agent contained in the composition under a wider variety of storage conditions, as it is recognized by those skilled in the art that lyophilized preparations are generally more stable than their liquid counterparts. Such lyophilized preparations are reconstituted prior to use by the addition of suitable pharmaceutically acceptable diluent(s), such as sterile water for injection or sterile physiological saline solution, and the like.